Detecting Cu2+ and H2O in methanol based on aggregation-induced emission fluorescent enhancement

A tridentate Schiff base probe L (2-NC5H4)C(H)=N(C6H4OH-2) was synthesized via a facile reaction. Probe L showed weak fluorescence emission that originated from intermolecular proton transfer in solution. With addition of Cu2+, the emission of L was quenched by the paramagnetic nature of Cu2+. However, after the solution of L and Cu2+ was refluxed, the emission presented a completely opposite result changing from fluorescent quenching to fluorescent enhancement. The fluorescent enhancement was attributed to a planar cis-structure of Cu2+ complex. Hence, a strategy for change of emission behavior of fluorescent probe L to Cu2+ was developed; a “turn on” mode of detection Cu2+ was realized in methanol solution. A simple refluxing made probe L work as a light-up fluorescent sensor for Cu2+ in methanol solution and gave improvement of sensitivity and selectivity in detection of Cu2+. When H2O was added into the solution of the Cu2+ complex, fluorescent enhancement increased and it can be used to detect water content in methanol.